In everyday conversation, the word “materialism” is used to refer to the desire for material goods. This is not, however, the way in which Marx uses the word. Instead, Marx uses the word “materialism” to refer to the idea that everything about society is determined by material causes, not by things like ideologies or the “spirit of the age.”
In Marx’s thought, the basis of all aspects of human society was material conditions. He argued that all people have to produce things in order to live. They set up systems that allow them to do this. There is typically a division of labor in which some people do one kind of job while others do other kinds of jobs. The system that each society sets up for procuring the things it needs is a material fact, not an idea.
Marx goes on to say that everything about a society is determined by the economic system that it sets up. He argues that there are a number of different stages of society, each with its own economic system. All feudal systems, for example, are the same. All capitalist systems are essentially the same. This is because all of the relevant aspects of their society are determined by what material system they have set up for satisfying their needs.
The idea that these systems determine the nature of societies is “materialism” in the Marxist sense of the word.